Device for welding plastic tubes

ABSTRACT

A device for welding plastic tubes includes a pair of tube holders each of which has a tube clamp which includes an upper jaw and a lower jaw. The jaws in both of the tube clamps of both tube holders have smooth tube contacting walls to permit the tubing to slip through either side when the tube holders and tubes are being moved from a loading station to a stripping station to increase the length of fluid free area in the clamped tubes,

BACKGROUND OF THE INVENTION

Various techniques have been used for welding plastic tubes particularlyas used in the medical field. U.S. Pat. No. 7,398,813 describes a devicehaving a first tube holder and a second tube holder. Each of the tubeholders has first and second parallel tube holding areas in line witheach other. In practice a first tube would be placed in the alignedfirst tube holding areas across the location where the tube holders areadjacent each other. A second tube would be similarly placed in thealigned second tube holding areas. A tube clamp in each of the firsttube holding areas clamps the first tube to create a generally fluidfree area of the first tube. A tube clamp is similarly provided in thesecond tube holding areas to create a generally fluid free area of thesecond tube. At least one of the clamps is laterally movable while theclamps are maintained in their clamping condition. To increase thelength of the fluid free area preferably both clamps of one of the tubeholders are laterally movable by having that tube holder movedlaterally. Such movement is performed after the tubes are initiallyloaded in a loading station, then the one tube holder is laterally movedin a stripping station to increase the size of the fluid free area.Thereafter, the tubes are cut. In U.S. Pat. No. 7,398,813 the cutting isdone with a non-heated cutting device, such as a cold blade, and thetube holders are then moved to a heating station while the clamps arestill maintained in their clamping condition. In the heating station aheating device heats/melts the cut stub ends of the tubes. The cut endsof the tubes are realigned so that a cut stub end of the first tubebecomes aligned with a cut stub end of the second tube and these twoaligned heated/melted cut stub ends are then shifted into contact witheach other to become welded together.

The specific arrangement for clamping the tubes disclosed in U.S. Pat.No. 7,398,813 includes clamp jaws of different construction in one tubeholder as compared with the other tube holder. More particularly thecompressed tubing is held tight by square jaws in one tube holder whilethe jaws in the other tube holder are smooth jaws to allow the tubing toslip through the smooth jaws.

SUMMARY OF THE INVENTION

An object of this invention is to provide a device for welding plastictubes which facilitates the clamped tubing to slip through the jawswhile in the clamped condition.

A further object of this invention is to modify the structure of theclamping jaws as compared to the structure disclosed in U.S. Pat. No.7,398,813.

In accordance with this invention the clamping jaws in both of the tubeholders are smooth jaws rather than one set of jaws being square jaws.This permits slippage of the tubing on either or both sides rather thanholding one of the tubes tight.

THE DRAWINGS

FIG. 1 is a top plan view of a device for welding plastic tubes inaccordance with this invention; and

FIG. 2 is a cross sectional view taken from FIG. 1 along the line 2-2.

DETAILED DESCRIPTION

The present invention is directed to devices for welding plastic tubes,such as disclosed in U.S. Pat. No. 7,398,813 and in the patents referredto in column 1 of U.S. Pat. No. 7,398,813. All of the details of U.S.Pat. No. 7,398,813 and the other patents referred to therein areincorporated herein by reference thereto.

FIGS. 1-2 illustrate a device 10 for welding plastic tubes. As shown inFIG. 1 device 10 includes a first tube holder 12 and a second tubeholder 14. Tube holder 12 includes first tube holding area 16 and aparallel second tube holding area 18. The tube holding areas may begrooves extending across the tube holder. Similarly, second tube holder14 includes first tube holding area 20 and second tube holding area 22which is parallel to tube holding area 20. These tube holding areas mayalso be grooves. The spacing between the tube holder areas 16 and 18 isthe same as the spacing between tube holding areas 20 and 22.

FIG. 1 illustrates the tube holders 12 and 14 in the loading station 24of the device 10. While in the loading station, a first tube T-1 isinserted in tube holding area 16 of tube holder 12 and in the alignedtube holding area 20 of tube holder 14. Similarly, a second tube T-2 isinserted in the aligned second tube holding areas 18 and 22. While inthese tube holding areas the tubes T-1 and T-2 are clamped and held inposition in each tube holder. FIG. 2 illustrates the clamping mechanism26 for tube holder 12 and the clamping mechanism 28 for tube holder 14.The lower half of the first tube holder 12 includes tube holding areasor grooves in which are mounted a lower jaw 30. An upper jaw 32 ispivotally mounted at one end of first tube holder 12. Jaw 32 is pivotedby manipulating handle 34 to move the jaw to and from its clampedcondition.

Similarly, clamp mechanism 28 for the second tube holder 14 includes alower jaw 36 and an upper jaw 38 pivotally connected to the lower jaw36. A handle 40 can be used to move the upper jaw into clampingrelationship with the lower jaw. The tube holding areas 20,22 are alsoformed in the lower half of the second tube holder 14.

After the tubes T-1 and T-2 are clamped in place in the loading station24, the tube holders 12,14 are jointly moved longitudinally by anysuitable structure such as screw 42 away from the loading station 24.Such movement is controlled by cam operation. FIG. 1 illustrates a camtrack 50 with two straight portions joined by curved portion 48. Cam 46rides in track 50. The tube holders 12, 14 carrying the clamped tubesare moved together in a longitudinal direction to a stripping station44. The cam has a slight outward bend in the track 50 that spreads thetube holders 12,14 apart at the stripping station stripping the fluidfrom the tubes prior to reaching a cutting blade in the cutting station52. The carriage carrying the tube holders then reverses direction andthe carriage and tube holders move completely up to the outer end of thetrack 50 to the heating/melting station 54. The cam 46 has a large rampthat separates the tube holders to allow them to clear the infraredheater coil and sets up the proper distance for melting. Once themelting is finished the tube holders 12,14 reverse direction and headback towards the original loading station 24 which is now the weldingstation. Upon passing the bend 48 the tube holders shift toward eachother. One of the tube holders is held in place while the other tubeholder is allowed to move longitudinally and realign the tube ends sothat the two tube lines will be welded together when the clamps closelaterally back together as they move pass the large ramp or bend 48 tothe welding station.

The description indicated above relates to steps which are alsoperformed in the procedures described in U.S. Pat. No. 7,398,813. Inthat patent, however, the jaws of the tube clamps are of a specificconstruction wherein the jaws for the second tube holder arespecifically designed to be square jaws so that the portions of thetubes T-1 and T-2 in the second tube holder 14 are held tight by thesquare jaws and the tubing is allowed to slip through smooth jaws in thefirst tube holder 12.

FIG. 2 illustrates the tube clamps 26 and 28 to have its jaws of a formwhich differs from that of U.S. Pat. No. 7,398,813. In that regard, asshown in FIG. 2, the lower jaw 30 for tube holder 12 has its tubecontacting wall 58 at the clamping portion to be of smooth continuouscurved configuration. Similarly, the upper jaw has its tube contactingwall 60 of smooth continuous curved configuration. The jaws for secondtube holder 14 have a similar construction and thus differ from the jawconstruction of U.S. Pat. No. 7,398,813 which utilizes square jaws.Accordingly, as shown in FIG. 2 the lower jaw 36 has its tube clampingportion 62 to be of smooth continuous curved configuration and also hasits upper jaw tube clamping portion 64 to be of smooth continuous curvedconfiguration.

By replacing square fixed jaws with smooth radius slip jaws there is noneed to hold one side of the tubing fixed. Instead, having smooth slipjaws on both tube holders 12 and 14 results in a number of distinctadvantages. For example, the fluid can be stripped back from either orboth sides. The tubing will slip through the side with the leastresistance. In addition, very small stub ends can be made. In thatregard, if hydraulic pressure in the stub end prevents the fluid frombeing stripped back on one side then the fluid will be stripped back onthe opposite side which has less or no back pressure. Further, there isless overall tubing area to be compressed when the clamping is done witha curved radius jaw as compared to a flat jaw.

Accordingly, the jaw configurations shown in FIG. 2 represent adistinctly different jaw configuration than that previously used whenmoving the first tube holder laterally away from the second tube holderduring a stripping action in a device for welding plastic tubes.

FIG. 1 illustrates the device 10 to have a cold cutting station 52 whichis displaced from the heating station 54. The invention, however, couldbe practiced where both stations are combined. For example, if the tubesare cut by a heated wafer, the cutting of the tubes also results inmelting the cut portions of the tubes to be in a condition for weldingonce the tubes are realigned and the heated ends are pressed intocontact with each other.

1. In a device for welding plastic tubes comprising a first tube holderhaving first and second parallel tube holding areas, a second tubeholder having first and second parallel tube holding areas which arealignable with said tube holding areas of said first tube holder wherebya first tube may be placed in the aligned first tube holding areas and asecond tube may be placed in the aligned second tube holding areas, saidfirst tube holder having a first tube clamp and a second tube clamp forrespectively clamping each of the tubes in the respective tube holdingareas, said second tube holder having a first tube clamp and a secondtube clamp for clamping each of the tubes in the respective tube holdingareas whereby a fluid free area is created in each tube, at least one ofsaid tube holders being laterally movable with respect to the other ofsaid tube holders while said tube clamps are in the clamping conditionto increase the length of fluid free area in each of the tubes to createan enlarged gap between said tube clamps of said first tube holder andsaid tube clamps of said second tube holder, the improvement being inthat each of said clamps in each of said first tube holder and saidsecond tube holder comprises an upper jaw and a lower jaw for pressingagainst the respective tube between said jaws, said jaws in said clampsof one of said tube holders having smooth tube contacting walls at theirtube clamping portion, and said jaws in said clamps in the other of saidtube holders having smooth tube contacting walls at their tube clampingportion, and each of said tube contacting walls being of smoothcontinuous curved configuration.
 2. The device of claim 1 wherein all ofsaid jaws in said first tube holder and in said second tube holder havesmooth tube contacting walls.
 3. (canceled)
 4. The device of claim 2wherein said device includes a tube loading station whereby the firstand second tubes may be loaded into said tube holders and then clampedat said loading station, a stripping station downstream from saidloading station wherein said at least one tube holder is shiftedlaterally, a cutting station downstream from said stripping station tocut through the first and second tubes, and a realignment station forrealigning the tubes so that a portion of one tube may be welded to aportion of the other tube.
 5. The device of claim 1 wherein said deviceincludes a tube loading station whereby the first and second tubes maybe loaded into said tube holders and then clamped at said loadingstation, a stripping station downstream from said loading stationwherein said at least one tube holder is shifted laterally, a cuttingstation downstream from said stripping station to cut through the firstand second tubes, and a realignment station for realigning the tubes sothat a portion of one tube may be welded to a portion of the other tube.6. In a method of welding plastic tubes comprising providing a firsttube holder having first and second parallel tube holding areas adjacentto a second tube holder having first and second parallel tube areas,placing a first tube in the aligned first tube holding areas of thefirst and second tube holders, placing a second tube in the alignedsecond tube holding areas of the first and second tube holders in aloading station, clamping the first tube and the second tube by a firsttube clamp in the first tube holder and a second tube clamp in thesecond tube holder to create a fluid free area in the tubes between thetube clamps, and moving the first and second tube holders and theclamped tubes from the loading station to a stripping station whileshifting the first tube holder laterally away from the second tubeholder, the improvement being in clamping the tubes by a tube clamp ofthe first tube holder and a tube clamp of the second tube holder witheach clamp having an upper jaw and a lower jaw and wherein each of thejaws has a smooth tube contacting wall, and increasing in length thefluid free areas of the first tube and the second tube as the first tubeholder is shifted laterally away from the second tube holder.
 7. Themethod of claim 6 wherein during the shifting of the first tube holderaway from the second tube holder permitting the tubes to slip throughthe respective tube clamp of the first tube holder or of the second tubeholder which has the least resistance.
 8. The method of claim 6including slipping the tubes through either or both of the clamping jawsof the first tube holder and of the second tube holder.